I’m 5’6 160lbs with athletic build. Normally wear a size medium with Nike and Adidas shirts. I was looking for similar sized shirts, so could have gone down a size here. Only problem is the waist is pretty loose. If you like it on the loose side then this will be fine for you. The sleeves were also a bit longer than I expected. Overall, the fabric is soft and comfortable to wear to sleep or around the house. It wasn’t what I expected so will be returning.